To make this more concrete: I sometimes look at Topics without a Category and ask myself if they would fit natually in the existing scheme. To pick on a recent example at random, the Topic Haskell wlroots bindings.
I understand the author to have an idea - that new Haskell bindings for the wlroots library would be valuable - and be seeking to spark some discussion about that.
A Category does two things: (1) it enables Topics to be grouped, reducing ‘search costs’ for users; and (2) it signals what the Haskell Community is for. I am assuming that one thing it is for is to surface ideas/suggestions in order to seek community views on them.